From 73425c31ce732646c6b2299feba4b913d9e93387 Mon Sep 17 00:00:00 2001
From: Sean Hayes <sean@seanhayes.name>
Date: Wed, 17 Feb 2016 04:59:53 -0800
Subject: [PATCH] Permit changing existing value on a ToOneField to None.
 (Closes #1449)

---
 docs/release_notes/dev.rst    |  2 +-
 tastypie/resources.py         | 12 ++++++++++--
 tests/core/tests/resources.py | 31 +++++++++++++++++++++++++++++++
 3 files changed, 42 insertions(+), 3 deletions(-)

diff --git a/docs/release_notes/dev.rst b/docs/release_notes/dev.rst
index 8ac649786..3b7387ade 100644
--- a/docs/release_notes/dev.rst
+++ b/docs/release_notes/dev.rst
@@ -7,4 +7,4 @@ copied to the release notes for the next release.
 Bugfixes
 --------
 
-* list of issues/PRs
+* Permit changing existing value on a ToOneField to None. (Closes #1449)
diff --git a/tastypie/resources.py b/tastypie/resources.py
index 6263e349a..486d76f51 100644
--- a/tastypie/resources.py
+++ b/tastypie/resources.py
@@ -25,6 +25,12 @@
 except (ImproperlyConfigured, ImportError):
     GeometryField = None
 from django.db.models.constants import LOOKUP_SEP
+try:
+    from django.db.models.fields.related import\
+        SingleRelatedObjectDescriptor as ReverseOneToOneDescriptor
+except ImportError:
+    from django.db.models.fields.related_descriptors import\
+        ReverseOneToOneDescriptor
 from django.db.models.sql.constants import QUERY_TERMS
 from django.http import HttpResponse, HttpResponseNotFound, Http404
 from django.utils import six
@@ -944,10 +950,12 @@ def full_hydrate(self, bundle):
                                 setattr(bundle.obj, field_object.attribute, value.obj)
                             except (ValueError, ObjectDoesNotExist):
                                 bundle.related_objects_to_save[field_object.attribute] = value.obj
+                        elif field_object.null:
+                            if not isinstance(getattr(bundle.obj.__class__, field_object.attribute, None), ReverseOneToOneDescriptor):
+                                # only update if not a reverse one to one field
+                                setattr(bundle.obj, field_object.attribute, value)
                         elif field_object.blank:
                             continue
-                        elif field_object.null:
-                            setattr(bundle.obj, field_object.attribute, value)
 
         return bundle
 
diff --git a/tests/core/tests/resources.py b/tests/core/tests/resources.py
index 4fab4f273..5802bb97e 100644
--- a/tests/core/tests/resources.py
+++ b/tests/core/tests/resources.py
@@ -542,6 +542,37 @@ def test_full_hydrate(self):
 
         self.assertEquals(hydrated.obj.name, "Daniel")
 
+    def test_full_hydrate__can_put_null_to_clear_related_value(self):
+        class RelatedBasicResource(BasicResource):
+            parent = fields.ToOneField(BasicResource, 'parent', null=True, blank=True)
+        basic = RelatedBasicResource()
+        basic_bundle_1 = Bundle(data={
+            'name': 'Daniel',
+            'view_count': 6,
+            'date_joined': None,
+            'parent': None
+        })
+        basic_bundle_1.obj = Mock()
+        basic_bundle_1.obj.date_joined = aware_datetime(2010, 2, 15, 12, 0, 0)
+        basic_bundle_1.obj.parent = Mock()
+
+        self.assertEqual(basic_bundle_1.data['date_joined'], None)
+        self.assertEqual(basic_bundle_1.data['parent'], None)
+        self.assertNotEqual(basic_bundle_1.obj.date_joined, None)
+        self.assertNotEqual(basic_bundle_1.obj.parent, None)
+
+        # Now load up the data.
+        hydrated = basic.full_hydrate(basic_bundle_1)
+
+        self.assertEqual(hydrated.data['name'], 'Daniel')
+        self.assertEqual(hydrated.data['view_count'], 6)
+        self.assertEqual(hydrated.data['date_joined'], None)
+        self.assertEqual(hydrated.data['parent'], None)
+        self.assertEqual(hydrated.obj.name, 'Daniel')
+        self.assertEqual(hydrated.obj.view_count, 6)
+        self.assertEqual(hydrated.obj.date_joined, None)
+        self.assertEqual(hydrated.obj.parent, None)
+
     def test_obj_get_list(self):
         basic = BasicResource()
         bundle = Bundle()